The Proportions and Movement of Slide Valves

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Technical Publishing Company, Limited, 1903 - 160 páginas
 

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Página 11 - Before dismissing the subject of loco-motive engines, it ought to be remarked, that they must always be objectionable on a rail-road for general use, where it is attempted to give them a considerable degree of speed ; for many pass-places there cannot be ; hence, the velocity of the greater part of the carriages on a line of road must be limited by a slow travelling one.
Página 11 - The angle in a semicircle is a right angle ; the angle in a segment greater than a semicircle is less than a right angle ; and the angle in a segment less than a semicircle is greater than a right angle.
Página 11 - ... inch, being produced by fixing the eccentrics a little in advance of the position at right angles to the cranks. It is found necessary to let the steam on to the opposite side of the piston before the end of the stroke, in order to bring it up gradually to a stop, and diminish the violent jerk that is caused by its motion being changed so very rapidly as five times in a second.
Página 11 - They would exist independently of matter, but their existence is no less positive, though immaterial. A system of geometry proceeds from simple, axiomatic, and incontrovertible principles, to the demonstration of new truths ; and from the combination of truths previously known, new truths are continually evolved, and thus a system of geometrical science is established by a continued process of logical deduction. Some of the elementary truths in geometry are so obvious as to be almost self-evident...
Página 11 - ... their having so small a heating surface, which was only about two and a half square feet for each foot of water evaporated per hour; the proportion in the present one being five and a half square feet, and in stationary engines as much as eight. " The great perfection of the present locomotives, and their superiority to the old ones, is caused not so much by the application of new inventions to them, as by the combination of many former ones, and the uniting together several plans which, separately,...
Página 34 - Description of the Patent Locomotive Steam Engine of Messrs. Robert Stephenson and Co., Newcastle-uponTyne," the slide valve used for a locomotive built for Messrs.
Página 11 - ... piston so quickly with the full pressure, and the regulator has to be only partially opened, so as to throttle the steam and check its passage into the cylinders ; which diminishes its pressure, as it has still to occupy the same space. The negative pressure of the waste steam amounts, for this reason, to 30 or 40 per cent, of the positive pressure of the steam upon the piston when the engine is running very fast, and the power of the engine is diminished nearly one-half.
Página 11 - ... obtain the maximum power by working expansively. But to obtain the greatest useful effect, the full pressure will require to be continued longer; and to an extent which depends on the quantity of friction of the additional machinery necessary to produce the useful effect. An engine ought to be made so that the communication between the cylinder and boiler could be cut off at any part of the stroke, from the one given in the table to full pressure, at the pleasure of the attendant, or according...
Página 11 - ... consequence of the lead of the slide, and acts expansively for that portion, saving so much of the steam, but diminishing the total power a little : the extent of this action is, however, very limited, as the piston is less than £ inch from the end of its stroke when the steam is shut off. In stationary and marine condensing engines the steam has usually very little or no lead, but it is shut off at two-thirds or three-quarters of the stroke, giving a great amount of expansive action, and the...
Página 11 - The waste-port is always covered by the slide, as the travel is less than the width of the bars, so that the steam is always prevented from entering the waste-port from the steam chest. During the reciprocating motion of the slide, each of the steamports is alternately uncovered, and the steam allowed...

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